SCA for reply to received SMS?

To be able to send an SMS, a device must have a valid Service Centre Address, SCA (aka Message Centre phone number, etc)

When reading a message in PDU mode, an SCA is included - Is it safe to assume that this SCA will be valid for use to send any reply :question:

From my experience you don’t need to specify the SCA with most operators nowadays anymore…

I agree - but most is not sufficient!